Yet the above hasn’t stopped scientists from scanning the heavens looking for potential sounds. For example, NASA found that sound can exist in the form of electromagnetic vibrations that pulsate in similar wavelengths. When Voyager 1 finally crossed into interstellar space in 2013, NASA was able to put together and play the sound of plasma wave data, which functioned as a kind of proof that the crossing occurred. A report last year from Scientific American showed that you can convert the hail of cosmic radiation into audible ‘music’ tracks, in an effort to better understand phenomena like the solar wind. It’s even believed that ancient sound waves may have sculpted the way galaxies formed, and that black holes may produce sound waves (pictured right).For centuries, mankind has been fascinated with the possible sounds of the heavens. We know that sound doesn’t travel in the vacuum of space — by definition, and unlike light, sound needs a medium through which to travel. Sound results from the disturbance (or vibration) of the particles in that medium. That’s why you hear those stories about how space battles in movies have impossible sound effects, because you wouldn’t hear any of it if it were real.
Now a team of researchers have found the first evidence that stars generate a sound of their own — although the result is distinctly otherworldly. At nearly a trillion hertz, the sound generated in the experiment wasn’t something fit for human enjoyment. (The human ear recognizes pitches from 20 to 20,000Hz.)
“One of the few locations in nature where we believe [the above effect] would occur is at the surface of stars,” said the University of York’s Dr. Pasley, who worked with scientists from the Tata Institute of Fundamental Research in Mumbai, India, and the Science and Technology Facilities Council’s Central Laser Facility in Oxfordshire. “When they are accumulating new material, stars could generate sound in a very similar manner to that which we observed in the laboratory — so the stars might be singing — but, since sound cannot propagate through the vacuum of space, no-one can hear them.”
To discover the effect, the researchers fired an ultra-intense laser at a small target of plasma. One trillionth of a second after the laser hit, plasma immediately flowed from high-density areas to more stagnant, lower-density area, in a kind of fluid traffic jam. As the plasma accumulated between the regions, it generated a series of pressure pulses — in another words, a sound wave, albeit at close to a trillion hertz.
“It was initially hard to determine the origin of the acoustic signals,” Dr. Alex Robinson, from the Plasma Physics Group at STFC’s Central Laser Facility, and who developed a numerical model to generate acoustic waves for the experiment, said in a statement. “But our model produced results that compared favorably with the wavelength shifts observed in the experiment. This showed that we had discovered a new way of generating sound from fluid flows. Similar situations could occur in plasma flowing around stars.”
None of this means that the next time you watch Gravity or Star Wars, you should believe the sounds you’re hearing in space are anything but impossible. But for the first time, it seems possible that not only the universe itself, but stars in particular, can produce sound after all.
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